Servbot #35 has the special skill of Painting. After obtaining the Paint Set from Servbot #2 in the Lab, take it to the Meeting Room and give it to #35 so that he will realize his skill and offer to paint the Gustaff in a variety of different color themes.

To start with, #35 will be able to paint the Gustaff in the Heroic, Hip-hop, Villainous and Cute looks, in addition to restoring it to its original colors. By collecting additional items and giving them to #35, you can inspire him to come up with even more styles for the Gustaff.

Bon Bonne look: Get the Bon Parts by talking to Servbot #13 in the Gym.
Teisel Bonne look: Get the Memento in a treasure chest deep within the Nakkai Ruins.
Dark look: Get the Flier from Servbot #24 up on the Deck of the Gesellschaft.
Stylish look: Get the handkerchief from #16 in Headquarters (after paying the 1 Million Zenny to Loath).